The All-Ceramic Knee Endoprosthesis—The Gap Between Expectation and Experience with Ceramic Implants

Total knee replacement (TKR) is a successful procedure in orthopedic surgery. In order to further improve survival rates and obtain optimal clinical outcome with higher range of motion, improvements in fixation and wear couples as well as specific designs have been made. The worldwide circulation of ceramics in total hip replacement is justified through its extreme wear and corrosion resistance because of the excellent tribological properties and the absence of electrochemical reactions. Using these advantages, as well as finding a solution in cases of hypersensitivity against metallic implant materials, led to the development of total knee replacement systems with ceramic components. However, ceramic materials are brittle and less resistant especially to impact load in comparison to metallic implants. This requires components with sufficient thickness on the tibial side, which can lead to increased bone loss. In particular, this may lead to inadequate stability and dislocation of the joint line. Furthermore, the tribological behavior of an all-ceramic total knee, i.e. the femoral and tibial component as well as the insert, is not clearly investigated so far. Therefore, all-ceramic knee endoprostheses are not feasible at the moment. There is still a need for further development and adequate preclinical testing of all-ceramic implants. Major prerequisite should be the optimization of existing designs of the femoral ceramic component.